Effects of temperature and habitat complexity on an urban tree pest (Tinocallis kahawaluokalani), natural enemies, and predation services in the city
Trees provide many ecosystem services in our urban environments. However, city trees are often stressed by pests and hot urban temperatures. Our research highlights how temperature affects a common tree pest, crape myrtle aphid (Tinocallis kahawaluokalani), natural enemies, and egg predation services on crape myrtles in the city. This research addresses an area of study that has largely been unexplored, effects of temperature on urban natural enemies, and it sheds light on how hot urban temperatures affect one species of piercing-sucking herbivore, a guild that is generally thought to be benefitted in hot city environments. To test our hypothesis that temperature increases T. kahawaluokalani density, fecundity and population growth, yet decreases natural enemy density and egg predation services on street trees, we collected data on crape myrtle trees in Raleigh, NC and conducted lab experiments in 2018. We collected canopy temperature and arthropod data on study trees from May–August and measured local structural complexity around trees and plant water potential. Aphid density decreased with hotter urban temperatures. However, natural enemies and egg predation were not affected by temperature. Natural enemy density was most correlated with local structural complexity. Together these findings suggest that increasing local structural complexity around trees may be a way to support natural enemies on both cool and hot urban trees. Our findings also emphasize the need for similar studies that evaluate temperature effects on common tree pests to help landscape managers prioritize pest targets for pest control in a warmer and more urban world.
KeywordsBiological control Aphids Natural enemies Urban trees Urban heat island
We thank Tom Wentworth, George Hess, and Michael Reiskind, who provided helpful advice along the way. We also thank Elsa Youngsteadt, Emily Griffith, and Michael Just for statistical guidance and feedback. We thank Matt Bertone, who provided helpful identification advice, as well as Annemarie Nagle, Leo Kerner, Cat Crofton, Ian McAreavy, Danielle Schmidt, Nicole Bissonnette, Aimee Dalsimer, Janis Arrojado, Kelly Harris, Logan Tyson, Doua Jim Lor, Tommy Pleasant, Anna Holmquist and all of the dedicated lab members who helped collect and analyze data for this project. This project was supported by Cooperative Agreement no. G15AP00153 from the United States Geological Survey to S.D.F. Its contents are solely the responsibility of the authors and do not necessarily represent the views of the Department of the Interior Southeast Climate Adaptation Science Center or the USGS. Funding for this work was also provided by U.S. Department of Agriculture, Grant Award Number: 2013-02476 to S.D.F. and the Southeast Climate Adaptation Science Center graduate fellowship awarded to S.E.P. The North Carolina State University Department of Entomology also contributed support for this research. North Carolina School of Science and Mathematics also contributed support for this research.
S.E.P and S.D.F conceived of experimental design. S.E.P. collected and analyzed the data. K.S.S. and A.A.W. collected data for lab experiments. All authors contributed to drafts and gave approval for publication.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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